At this point he starts to laugh uncontrollably before saying with a slight slur: "There's video on Instagram."

“So, crazy news!”

Justin Bieber

And that's pretty much it - obviously that news is the funniest thing Justin has heard all day.

The video prompted Twitter speculation that he was stoned.

One tweeted: "Justin Bieber was definitely stoned in that Instagram video," while another directly tweeted Justin saying: "admit that you were stoned while you watched it because everyone knows you were high enough to dunk.”

Maybe he just finds the news of social media sites introducing video features funny?!